danger to her hostess; who, timely warned, shuts her door and keeps out the enemy. When the crab has, unmolested, succeeded in loading itself with provisions, it gives a signal by a gentle noise at the opening of the shell, and when admitted, the two friends feast together on the fruit of its industry. It would appear an arduous, nay, a task almost impossible for the defenceless and diminutive crab, not merely to elude its enemies and return home, but likewise obtain a supply of provender sufficient to satisfy the wants of its larger companion. The following different account of the nature of this alliance is more credible:—
Whenever the pinna ventures to open its shell, it is immediately exposed to the attacks of various of the smaller kinds of fish, which, meeting with no resistance to their first assaults, acquire boldness and venture in. The vigilant guard, by a gentle bite, gives notice of this to his companion, who, upon such a hint, closes her shell, and having thus shut them in makes a prey of those who had come to prey upon her: when thus supplied with food, she never fails to share her booty with so useful an ally.
We are told that the sagacious observer, Dr. Hasselquist, in his voyage, (about the middle of the last century,) to Palestine, which he undertook for objects connected with the study of natural history, beheld this curious phenomenon, which, although well known to the ancients, had escaped the attention of the moderns.
It is related by Aristotle[1] that the pinna keeps a guard to watch for her, which grows to her mouth, and serves as her caterer: this he calls pinnophylax, and describes as a little fish with claws like a crab. Pliny observes[2], that the smallest species of crab is called the pinnotores, and being from its diminutive size liable to injury, has the prudence to conceal itself in the shells of oysters. In another place he describes the pinna as of the genus of shell-fish, with the further particulars that it is found in muddy waters, always erect, and never without a companion, called by some pinnatores, by others pinnophylax;
